Personally, I would stay away from anything like a round-column Mill-Drill. Without generalizing too awfully much, they have a tendency to move under a heavy cut. Furthermore, they are constantly out of tram when attempting to change height.
Stainless is demanding stuff for a precision cut such as a 1911 frame, or any gun part for that matter. Such work demands great rigidity in a machine which usually means more weight.
My preference for gun work would include at the very least a moveable knee so that the head would not need to be re-trammed each time it's moved. It's very difficult to get the rigidity and repeatability that good mill work requires in a bench-top machine. It can be done but it requires a great deal more work.
By way of establishing my credentials to make such statements, I owned an H.F. Round Column Mill Drill for nearly ten years and recently replaced it with a Taiwanese Bridgeport Clone. The difference has been a real eye-opener to me. Part of the difference is 3,500 pounds sitting on a rock-solid heavy cast-iron base versus 750 pounds on a thin metal stand.
I know that great work can be done on machines as small as the three-in one H.F. units and even Sherline machines. Some of those have even been converted to CNC successfully. Nonetheless, I think a knee mill of some sort would be more suitable. My comments represent my own observations and my own opinion. Someone else may have a different take on this and it's fine with me.
